1. Field
The present disclosure generally relates to composite pressure vessels having liners, and deals more particularly with a dis-bond membrane that prevents bonding between the composite pressure vessel and the liner.
2. Background
Several types of constructions are known for high pressure vessels used to store liquids or gases such as hydrogen, for example. In one type of construction, commonly referred to as a Type IV pressure vessel, a plastic inner liner is surrounded by an outer structural wall formed by a fiber reinforced resin wrap. These types of pressure vessels are typically cylindrical in shape with domed ends. The pressurize vessels are cyclically pressurized, both as part of the fabrication process, and later, when placed in service.
The mechanical performance of the pressure vessel may depend upon the compatibility of the materials used for the liner and structural outer wall, and the processes used to fabricate the vessel. For example, where the liner is formed of a thermoplastic and the structural outer wall is formed of a thermoset that is in contact with the thermoplastic, undesired stress concentrations in the vessel may result from co-mingling of the thermoplastic with the reinforcing fibers used in the wall. This co-mingling occurs when the temperature at which the thermoplastic softens and/or melts is below the cure temperature of the thermoset resin used in the wall. During curing of the thermoset resin outer wall, the thermoplastic liner softens to the point that it flows or migrates into the wall. When the thermoset wall cools following curing, the migrated thermoplastic may cover and surround some of the reinforcing fibers of the wall, causing random bonds to be formed between the liner and the outer wall. These random bonds create undesired stress points when the liner expands and contracts during use. The presence of these stress points between the liner and the outer wall may reduce the performance of the pressure vessel.
Accordingly, there is a need for a method of fabricating a pressure vessel that reduces or eliminates bonding between an inner thermoplastic liner and a thermoset outer wall. There is also a need for a dis-bond barrier, and a simple method for installing the barrier between the liner and the outer wall.